1. Technical Field
The present invention relates to a slide operation device in which a moving block slides on a slide bar manually or electrically in a linear magnetic encoder, and an electrical parameter is set in accordance with a movement amount or absolute position of the moving block as a measurement value.
2. Background Art
This type of slide operation devices include the one disclosed in Japanese Patent Laid-Open No. 2006-49302. The slide operation device disclosed in Japanese Patent Laid-Open No. 2006-49302 is used as a fader of a mixing console, for example, and is configured such that a moving block moves along a guide body by manual operation of a slide operator. The moving block is held slidably by a main movement guide body and an auxiliary movement guide body in parallel with each other. The auxiliary movement guide body comprises a non-magnetic stainless shaft formed by insertion-molding of a magnetic material. And by detecting a magnetic polar pattern formed on the magnetic material by a magnetic sensor provided in the moving block, a position of the slide operator is detected, and the electric parameter is set in accordance with its movement amount as a measurement value.
If the movement guide body holding the moving block is made as a magnetic scale body, the entire movement guide body could be formed from a permanent magnetic material, but actually magnetic alloys are expensive and ferrites are fragile and have a problem in durability. On the other hand, if the movement guide body is mainly constructed by a substantially rod-shape shaft (slide bar) made of a non-magnetic stainless, it would be excellent in durability as a guide body.
However, in the above prior art, since the movement guide body is constituted by embedding a magnetic member (magnetic scale material) in a groove formed along the longitudinal direction of the non-magnetic stainless shaft (slide bar), there is a possibility that a part of the magnetic member is separated from the shaft by use for a long time. Particularly, the magnetic member tends to separate from the end portion of the shaft. Also, if the shaft is firmly fixed at the both ends to a case, there is a problem that the magnetic member is displaced in the longitudinal direction and becomes susceptible to separation due to a difference in linear expansion coefficient between the shaft and the magnetic member. Moreover, if the shaft is firmly fixed to the case at the both ends, there is a problem that the shaft is deformed in a direction crossing the axis due to thermal stress and an appropriate gap between a magnetic sensor and the magnetic member cannot be ensured, which causes lowered accuracy.